PROJECT SUMMARY/ABSTRACT Friedreich's ataxia (FRDA/FA) is the most commonly inherited autosomal recessive neurodegenerative disease for which there is no cure. This debilitating and ultimately lethal disease occurs due to reduced expression of frataxin (FXN), a nuclear encoded protein that plays a role in iron metabolism in mitochondria. Homozygous expansion of GAA triplet repeats in the first intron of FXN silence mRNA synthesis. The resulting FXN protein deficiency leads to progressive neurodegeneration, hypertrophic cardiomyopathy and even diabetes mellitus. A novel class of synthetic transcription elongation factors (Syn-TEFs) that target GAA repeat expansions in FXN and actively stimulate Pol II function across the silenced gene were recently developed by our group. In patient- derived cells, Syn-TEF1 restores FXN to levels observed in healthy individuals. The premise that underlies this proposal is that systematic evaluation of the Syn-TEF responsive changes in the epigenetic landscape and/or the formation of stable unusual DNA structures will reveal the extent to which of these mechanisms contribute to FXN silencing in patient-derived cells. This understanding will result in more mechanistically-guided design of the next generation precision-tailored Syn-TEFs. Moreover, testing Syn-TEFs in cell types where FXN deficiency results in ataxia and morbidity is a first step toward the development of genome-targeted precision therapeutics.